According to a technique disclosed by JP2011-085230A, an insert ring is provided to a pressure vessel. In JP2011-085230A, the insert ring is buried in a liner formed around a protrusion of a ferrule. The protrusion of the ferrule forms a part of the ferrule and is a cylindrical part formed in internal space.
In JP2011-085230A, sufficient consideration is not given to dissipation of heat in the internal space of the pressure vessel to the outside. During filling of the pressure vessel with gas, the temperature of the gas is increased by adiabatic compression. Hence, promoting heat dissipation from the internal space is preferred. In consideration of the above-described issue, this disclosure is intended to promote heat dissipation from internal space of a pressure vessel to the outside of the pressure vessel.